If your looking to single hand spey to keep your fly in the drink longer, and are fishing smaller streams (i'm not familiar w/ the ones you mentioned), you cant beat a triangle or DT line. WF lines are pretty much for overhead casting only. Sure- you can spey cast them, butthe advantages of the other two far outweigh WF lines in small streams. DT and tri's SH spey much better, and are easier to mend, and are easier to present w/ a softer landing. Depending on the action of your 5wt, an Ambush 5wt (215 grains I think) will sling pretty much anything out there. When you get the hang of it, you'll be able to shoot up to 25-30 of the running line (if need be). I use both, and love them. These lines really shine w/ the spey cast. I only use WF lines from the drift boat, or stillwater stuff.

Another line along the lines of what KWB had suggested is the Wulff Long Belly line, its essentially like a long belly spey line but designed for single hand rods. I WOULD NOT use a 9wt line on your 5wt!

Wulff Triangle Taper will do it just fine but so will a good old standard Double Taper. Add a haul and you can shoot a cress bug or bugger/sculpin straight across Breeches.

I agree. With a single handed 5 wt there's no specific need for a spey line. It's really just a variation of a long-belly WF. It would work fine, but I don't think it would offer any noticeable advantage over any other long-belly WF line or a DT line.

More generally, any long-belly WF or DT will give you better control than a standard WF for roll casting and line mending at distances beyond the length where a standard WF head begins to taper down to the running line. If you're not working beyond the head length of a WF, it would depend on the front taper designs of the particular lines you are comparing, but you probably wouldn't notice much difference at all.